Usage note

Both more important and more importantly occur at the beginning of a sentence in all varieties of standard English: More important (or More importantly), her record as an administrator is unmatched. Today, more importantly is the more common, even though some object to its use on the grounds that more important is an elliptical form of “What is more important” and that the adverb importantly could not occur in such a construction. More importantly probably developed by analogy with other sentence-modifying adverbs, as curiously, fortunately, and regrettably.